Also desperately looking for a solution to this, though due to SID format files as in message 6, connected with FDO in Civ3D LD Companion 2008. Sometimes the temporary PNG files disappear on their own, sometimes they don't. What I really need is a way to remove the endless phantom "! Unreferenced" entries from the External References palette (see screen capture) that point to temporary PNG files long since vanished. Unloading, detaching, purging, -purge regapps, classicimage detach, disconnecting FDO, deleting FDO - all fruitless. I've attached a typical dwg as well.
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